Hi Alasdair,
Thank you for the comments.
Alasdair G Kergon wrote:
Make sure you test this properly under low memory situations.
OK.
dm_swap_table() mustn't block waiting for memory to become
free (except in a controlled way e.g. with a mempool, but
it would need more than that here).
Here, dm_swap_table() leads to kmalloc() getting called
in sysfs_add_link().
I moved the sysfs_add_link() to the last part of dm_resume().
Directory creation/deletion are also moved in the alloc_dev/
free_dev function as kobject_register/unregister may allocate
memory.
I didn't change the part of removing symlink as it doesn't
allocate memory.
Do you think this is an acceptable approach?
--
Jun'ichi Nomura, NEC Solutions (America), Inc.
Exporting stacked device relationship to sysfs (dm)
Signed-off-by: Jun'ichi Nomura <[email protected]>
--- linux-2.6.15.orig/drivers/md/dm.c 2006-01-02 22:21:10.000000000 -0500
+++ linux-2.6.15/drivers/md/dm.c 2006-02-17 16:27:38.000000000 -0500
@@ -98,6 +98,12 @@ struct mapped_device {
*/
struct super_block *frozen_sb;
struct block_device *frozen_bdev;
+
+ /*
+ * sysfs deptree
+ */
+ int sysfs_linked;
+ struct kobject slave_dir;
};
#define MIN_IOS 256
@@ -791,6 +797,7 @@ static struct mapped_device *alloc_dev(u
md->disk->private_data = md;
sprintf(md->disk->disk_name, "dm-%d", minor);
add_disk(md->disk);
+ stackdev_init(&md->slave_dir, &md->disk->kobj);
atomic_set(&md->pending, 0);
init_waitqueue_head(&md->wait);
@@ -815,6 +822,7 @@ static void free_dev(struct mapped_devic
free_minor(md->disk->first_minor);
mempool_destroy(md->tio_pool);
mempool_destroy(md->io_pool);
+ stackdev_clear(&md->slave_dir);
del_gendisk(md->disk);
put_disk(md->disk);
blk_put_queue(md->queue);
@@ -841,6 +849,42 @@ static void __set_size(struct mapped_dev
up(&md->frozen_bdev->bd_inode->i_sem);
}
+/* create sysfs symlinks between mapped device and underlying devices */
+static int __link_device(struct mapped_device *md, struct dm_table *t)
+{
+ struct list_head *d, *devices;
+
+ if (md->sysfs_linked)
+ return 0;
+
+ devices = dm_table_get_devices(t);
+ for (d = devices->next; d != devices; d = d->next) {
+ struct dm_dev *dd = list_entry(d, struct dm_dev, list);
+ stackdev_link(dd->bdev, &md->slave_dir, &md->disk->kobj);
+ }
+
+ md->sysfs_linked = 1;
+ return 0;
+}
+
+/* remove sysfs symlinks between mapped device and underlying devices */
+static int __unlink_device(struct mapped_device *md, struct dm_table *t)
+{
+ struct list_head *d, *devices;
+
+ if (!md->sysfs_linked)
+ return 0;
+
+ devices = dm_table_get_devices(t);
+ for (d = devices->next; d != devices; d = d->next) {
+ struct dm_dev *dd = list_entry(d, struct dm_dev, list);
+ stackdev_unlink(dd->bdev, &md->slave_dir, &md->disk->kobj);
+ }
+
+ md->sysfs_linked = 0;
+ return 0;
+}
+
static int __bind(struct mapped_device *md, struct dm_table *t)
{
request_queue_t *q = md->queue;
@@ -873,6 +917,7 @@ static void __unbind(struct mapped_devic
write_lock(&md->map_lock);
md->map = NULL;
write_unlock(&md->map_lock);
+ __unlink_device(md, map);
dm_table_put(map);
}
@@ -1139,6 +1184,8 @@ int dm_resume(struct mapped_device *md)
dm_table_unplug_all(map);
+ __link_device(md, map);
+
r = 0;
out:
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